1. Field of the Invention
This invention relates to a combination structure of an electronic equipment including an electrical control circuit portion and a power circuit portion for providing electric power.
2. Description of the Related Art
Electronic control units (ECUs), each provided in a combined manner as a unit in accordance with the function of an object to be controlled, have heretofore been mounted on a vehicle. Each of the ECUs includes a control circuit portion (including a microcomputer or the like) for effecting a logical control operation, and a power circuit portion for controlling power to be fed to an exterior.
FIG. 15 roughly shows a combination structure of a conventional electronic control unit 1. Main portions of the electronic control unit 1 are contained in a connector-incorporating resin casing 2. A control connector 3 and power connectors 4 and 5 are provided in a gathered manner on one side surface of the connector-incorporating resin casing 2. With this construction, the connection to the electronic control unit 1 can be effected only from one direction. A plurality of power parts 6 and 7 are mounted within the connector-incorporating resin casing 2, and also connection terminals 8 and 9 are provided within the connector-incorporating resin casing 2. The connection terminals 8 and 9 are adapted to be electrically connected to a control board 10. The control board 10 is attached to the upper side of connector-incorporating resin casing 2, and has through holes 11 and 12 adapted to be electrically connected to the connection terminals 9 and the connection terminals 8, respectively. A plurality of control parts 13, 14 and 15 are mounted on the control board 10. A lid 20 is fitted on the casing 2 to cover the control board 10. A heatsink 21 is attached to the bottom of the connector-incorporating casing 2. A waterproof packing 22 is provided at a region of connection between the lid 20 and the connector-incorporating casing 2, and a waterproof packing 23 is provided at a region of connection between the connector-incorporating casing 2 and the heatsink 21.
In the combination structure shown in FIG. 15, the control board 10 is fixedly secured to the connector-incorporating casing 2 having the power parts 7 and 8 and so on mounted therein, and the control connector 3 and the power connectors 4 and 5 are formed integrally with the connector-incorporating casing 2. Therefore, the connector-incorporating casing 2 has a complicated construction, and can not be easily formed, and besides the assembling operation is difficult. JP-A-7-297561 discloses the conventional art concerning a box member of an electronic equipment in which a control circuit portion, a drive circuit portion and a power circuit portion are provided separately from one another in a manner to provide separate spaces. Radiating fins are mounted on the power circuit portion so as to prevent the temperature of the box member of the electronic equipment from rising. The circuit portions, which are different in signal level from one another, are separated from one another so as to reduce the rate of occurrence of malfunction due to noises. Signal input-output elements of the drive circuit portion are disposed near to signal input-output elements of the power circuit portion, and the two circuit portions are electrically connected directly to each other. However, the electrical connection between the drive circuit portion and the control circuit portion is made by a pair of connectors. Therefore, this structure can be regarded as being of the type in which the control circuit portion and the power circuit portion, including the drive circuit portion, are combined together.
In the combination structure shown in FIG. 15, the power connectors 4 and 5 and the control connector 3 are formed integrally with the connector-incorporating resin casing 2, and therefore the connector-incorporating resin casing 2 has a complicated construction, and can not be easily formed, and besides the assembling operation is difficult. Particularly when the connectors are increased in size and when the number of memories increases, it is difficult to provide the connectors on the same side surface of the connector-incorporating resin casing 2. The electronic control unit 1 is electrically connected to the exterior via wire harnesses, and when all of the connectors are not provided on the same side surface, the wire harnesses can not be easily arranged and installed, so that an installation space is increased. And besides, the packing 22 is used between the lid 20 and the casing 2, and also the packing 23 is used between the casing 2 and the heatsink 21, and this increases the production cost.
In the structure disclosed in JP-A-7-297561, the control circuit portion is connected to the drive circuit portion and the power circuit portion by the connectors, and therefore parts of these circuit portions need to be electrically connected to the connectors, and the amount of wires, used in each circuit portion, increases.
Conventionally, a large amount of heat is generated at bus bars which are near to connector pins of the connectors 4 and 5 attached to the power circuit portion of the electronic control unit 1 and which are connected to the connection terminals 8 and 9, in which a large electric current flows. The heat generated near to the connector pins or at the bus bar portion is radiated by the heatsink 21 fixed to the bottom surface of the connector-incorporating resin casing 2. The increase of the heatsink 21 in size can improve the heat radiation efficiency so that the control circuit portion is not adversely affected by heat. However, the increase of the heatsink 21 in size results in the increase of the total size of the electronic control unit 1, which makes the size reduction of the electronic control unit 1 difficult. Moreover, use of the large heatsink increases the manufacturing cost of the electronic control unit 1, which is inconvenient for the maker.